1. Field of the Invention
The present invention relates to a pure water reusing system for recovering and regenerating water discharged from an apparatus in which pure water is used, e.g., a polishing apparatus for polishing a substrate such as a semiconductor wafer, and supplying the regenerated pure water to an apparatus in which pure water is used.
2. Description of the Related Art
A large amount of pure water is used in a semiconductor fabrication plant. The production of pure water is expensive, and the disposal of used pure water as waste water results in increased cost. Therefore, in order to reduce the cost, a water reusing system has heretofore been used for recovering and regenerating water discharged from an apparatus in which pure water is used, and reutilizing the regenerated pure water. According to this conventional water reusing system, water discharged from all apparatuses used in all production processes is collected and regenerated in a batch process. Therefore, the conventional water reusing system involves the following problems.
If water discharged from different production processes is mixed, by-products are generated due to the adverse effect of impurities contained in the waste water. Further, since various kinds of waste liquid such as acidic liquid or alkaline liquid are mixed with waste water, a large number of steps are required in order to process and regenerate the recovered waste water. Furthermore, it is necessary to recover and regenerate the waste water respectively in separate devices, thereby increasing the scale of the processing facilities.
Further, in the conventional reusing system, the regenerated pure water is supplied to respective apparatuses through a common supply line. Therefore, the regenerated pure water cannot be supplied from the reusing system to the respective apparatuses while the pressure of the regenerated pure water is independently controlled for each of the apparatuses.
The present invention has been made in view of the above drawbacks. It is therefore an object of the present invention to provide a pure water reusing system which can simplify a process for regenerating water recovered from an apparatus in which pure water is used, and can supply the an apparatus in which pure water is of the regenerated pure water is controlled for each of regenerated pure water regenerated pure water to used while the pressure independently supply lines.
In order to attain the above object, according to one aspect of the present invention, there is provided a pure water reusing system for recovering water discharged from apparatuses in which pure water is used, and regenerating the water to produce pure water. The system comprises a recovering and regenerating apparatus for recovering water discharged from the apparatuses and regenerating the water by removing impurities from the water to produce pure water, the same process being conducted in the apparatuses in which pure water is used, and a regenerated pure water supply line for supplying the regenerated pure water to at least one of the apparatuses. The regeneration of water is to regenerate water to produce pure water.
Thus, an apparatus in which pure water is used and from which pure water is recovered and an apparatus in which pure water is used and to which the regenerated pure water is supplied are utilized for the same production process. Therefore, water to be recovered can be prevented from being contaminated by undesired waste water or chemical liquid. Further, a processing process in a regeneration device can be simplified to reduce the size of the regeneration device. Furthermore, since the apparatuses are utilized for the same process, it is not necessary to increase the purity of the regenerated pure water to a high level.
According to a preferred aspect of the present invention, the pure water reusing system further comprises at least one regenerated pure water supply line, and a supply pressure control mechanism for supplying the regenerated pure water at an independent water pressure for each of the regenerated pure water supply lines.
With the supply pressure control mechanism, the regenerated pure water can be supplied at a pressure suitable for operating conditions of the apparatus in which pure water is used and to which the regenerated pure water is supplied. Further, the regenerated pure water can be utilized for a process requiring pure water having a pressure higher than that in the normal process.
According to another preferred aspect of the present invention, the supply pressure control mechanism is capable of varying the supply pressure of the regenerated pure water in response to a signal from at least one of the apparatuses.
Since the supply pressure control mechanism can vary the supply pressure of the regenerated pure water in response to a signal from the apparatus in which pure water is used, the regenerated pure water can be supplied at a desired pressure according to required conditions, so that each of the apparatuses in which pure water is used can utilize the pure water under optimal operating conditions.
According to still another preferred aspect of the present invention, a pure water reusing system further comprises a switch valve for switching a passage of the water discharged from at least one of the apparatuses between a recovery line for recovering the water and a waste water line for discharging the water, wherein the passage of the water is switched between the recovery line and the waste water line according to condition of the water discharged from the at least one of the apparatuses.
Thus, the passage of the water is switched between the recovery line and the waste water line according to the condition of the water discharged from the apparatus in which pure water is used. Therefore, water contaminated by impurities and unsuitable for recovery can be prevented from flowing into the recovery line, thus improving the operating efficiency of the system.
According to another aspect of the present invention, there is provided a polishing system for polishing a substrate. The polishing system comprises a polishing apparatus for conducting a polishing process of a substrate using pure water, a water recovery section for recovering water used in the polishing process, and a recovery line for allowing the water used in the polishing process to flow into the water recovery section.
According to a preferred aspect of the present invention, the water recovery section recovers water which has been used for a predetermined process.
According to another preferred aspect of the present invention, the polishing system further comprises a regeneration section for regenerating the water recovered by the water recovery section to produce pure water.
In this case, it is desirable that a pair of the water recovery section and the regeneration section is provided for a plurality of polishing apparatuses. Preferably, at least one of the water recovery section and the regeneration section comprises a sensor for detecting whether the water is suitable for regeneration. In this case, the sensor may comprise one of an optical turbidimeter, a pH meter, and a particle counter.
According to still another preferred aspect of the present invention, the regenerated pure water is utilized for dressing a polishing surface which contacts a substrate to polish a surface of the substrate.
According to another preferred aspect of the present invention, the polishing apparatus further comprises a recirculating line for allowing water to be circulated through the water recovery section and the regeneration section and the polishing apparatus. In this case, a sensor for measuring the flow rate of water in the recirculating line may be provided. Further, it is desirable that the recirculating line comprises a supplementary pure water line for adding supplementary pure water to the regenerated pure water.
According to still another aspect of the present invention, there is provided a method for polishing a substrate. The method comprises conducting a polishing process of a substrate using pure water, and recovering water which has been used for the polishing process.
According to a preferred aspect of the present invention, the method for polishing a substrate further comprises regenerating the recovered water to produce pure water. In this case, it is desirable that the method further comprises dressing a polishing surface with the regenerated pure water.
The above and other objects, features, and advantages of the present invention will be apparent from the following description when taken in conjunction with the accompanying drawings which illustrates preferred embodiments of the present invention by way of example.